Humans generally perceive their environment through five traditionally recognized senses—sight or vision; hearing or audition; taste or gustation; smell or olfaction; and touch or somatosensation. The ability to detect other stimuli beyond those governed by these five most broadly recognized senses also exists. These sensory modalities include: temperature or, thermoception or thermoreception; kinesthetic sense or proprioception; pain or nociception; balance or equilibrioception; vibration/pressure or mechanoreception; and various internal stimuli, for example, the different chemoreceptors for detecting salt and carbon dioxide concentrations in the blood, or sense of hunger and sense of thirst.
Although the origins of virtual reality can be traced back more than one hundred and fifty years, the exact origins are in dispute, in part, due to difficulty in defining the concept of an alternative existence. Elements of virtual reality appeared as early as the 1860s. The first of what might be referred to as wide-spread “virtual reality systems,” typically centered around the use of projected images with accompanying sound, i.e., sight and sound, to create a virtual environment. However, including only sight and sound, these systems were limited in their immersive nature, or “immersivity,” or limited in the sense of being able to give a person a sense of truly being “in” the virtual environment.
Today, due to the general availability and widespread use of computers, virtual reality can be defined as a computer technology that recognizes these basic senses and sensory modalities, and that uses various devices to provides stimuli associated therewith, to create a virtual or an imaginary environment. Still, many modern virtual reality systems are often limited to virtual reality headsets and accompanying auditory systems that provided sight and sound stimuli to create a virtual or imaginary environment. However, again, being limited to sight and sound, these systems are, likewise, not particularly immersive—offering a person a sense of being “in” the virtual environment. To this end, other virtual reality systems have been expanded to include the transmission of vibrations and other sensations to the user through, for example, a game controller, and are known as haptic systems, the tactile or touch related information generally known as forced feedback in gaming, medical, and military training applications.
Haptic communication is non-verbal communication, and refers to the ways in which people and animals communicate and interact using the sense of touch. In virtual reality systems, “haptics” refers to the science of applying touch sensations and controls to interactions with computer applications. Haptics offers an extra dimension to virtual reality environments and is essential to the feeling of true immersion in those environments, and are most commonly found in the use of vibration or electrostatic shock in contact with the skin. Today, in virtual or augmented reality systems using haptic feedback technologies, the dimension of thermoreception is largely omitted. Again, haptic feedback is mainly focused on the kinesthetic sense and/or mechanoreception, mimicking pressure.
Thermoception or thermoreception is the sense by which people and animals perceive temperature. The details of how temperature receptors in people and animals work is still being investigated. However, different materials are typically perceived to be at different temperatures, even if they are, in fact, at the same temperature. For example, when a person touches a piece of wood and a piece of metal, both of which are at the same temperature, the metal generally feels colder than the wood. This is due to the different materials or, in this example, wood and metal, having different thermal transfer properties. Further, this is also important for a person's tactile sensation of coming into contact with liquid. There is no known particular type of nerve ending for sensing a liquid. Rather, liquids are recognized as a combination of kinesthetic and/or mechanoreception and thermoreceptive stimuli.
Accordingly, there is a need for a technology that can simulate the sensation of touching materials with different thermal properties, allowing for a more immersive virtual haptic, tactile environment.